Blood Flow, Needle Size and Hemolysis — Examining an Old Wives' Tale

Abstract

TO avoid hemolysis during blood sampling, the admonition has been, "Use a larger bore needle." Theoretically, experimentally and in our clinical experience, the reverse is true. To test this hypothesis, an experimental determination of the relation between needle size and hemolysis was performed.MethodsThe blood to be examined was drawn from a dog whose stable, circulating red cells were "tagged" with 51Cr (25,000 to 100,000 cpm per milliliter) as previously described.† Hemolysis was calculated from the appearance of the radioactive label in the serum or plasma.The external jugular vein was catheterized under anesthesia with 5 cm (2 in) . . .